A separator that separates impurities from gas including the impurities is known. For example, the device disclosed in PTL 1 is provided with a separation chamber between a primary side port into which gas before treatment flows and a secondary side port from which gas after treatment is discharged. A filter element manufactured by shaping non-woven resin fabric into a cylindrical form is arranged in the separation chamber to introduce gas before treatment into the hollow part of the filter element. Then liquid such as moisture included in the gas before treatment is captured by the filter element and separated from the gas, and thus gas after treatment that has flowed out from the outer surface of the filter element is guided to the secondary side port.